Under similar conditions, which gas diffuses most rapidly through a small opening?
a. Methane, CH4
b. Carbon dioxide
C. Sulfur dioxide
d. Oxygen
e. Chlorine

The answer might be carbon dioxide

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.